1. Field of the Invention
The present invention relates to a safety photoelectric switch.
2. Description of the Background Art
As seen in Japanese Patent Application Laid-Open No. H4-310890 and Japanese Patent Application Laid-Open No. H3-175390, an optical scanning type photoelectric switch is known which two-dimensionally performs scanning with light to detect an object while detecting a position of this object. As also referred to as a safety scanner, a safety laser scanner, and the like, this optical scanning type photoelectric switch provides a protection area around a machine, a robot or the like as a danger source, and outputs to the danger source a safety signal not permitting its operation when an operator or the like enters this protection area.
Since this optical scanning type photoelectric switch scans a two-dimensional plane in a broad range, when another photoelectric switch is present adjacently thereto, a problem of interference with this another photoelectric switch tends to occur. Since the optical scanning type photoelectric switch measures a distance to the object based upon a time difference between a light projection timing of a light projection pulse and a light reception timing of reflected light from the object, when interference with another photoelectric switch occurs, the optical scanning type photoelectric switch may measure a distance to the object, which is different from an actual distance thereto. Needless to say, the optical scanning type photoelectric switch is safety equipment, and supplies the danger source with an operation non-permitting signal when the operator enters the protection area set around the danger source. Accordingly, for the optical scanning type photoelectric switch, the occurrence of the interference with another photoelectric switch is a problem that should be avoided, and in the conventional techniques, an installed height or an installed position of the optical scanning type photoelectric switch is adjusted, thereby to avoid this interference problem.